1. Field of the Invention
The present invention relates to an apparatus for measuring a flow amount of a medium.
2. Description of Related Art
An apparatus for measuring a flow amount of a medium is used for several industrial fields. For example, the apparatus is used for measuring a flow amount of gaseous fluid such as air flowing in an intake pipe of an internal combustion engine or flowing toward a burner, and gas flowing through a gas meter for metering amount of gas consumption. The apparatus is also used for measuring a flow amount of liquid fluid.
In such the apparatus, it is important to protect a sensing element from dust such as foreign particles, sand, contaminants, oily or greasy adhesive particles and micro carbon particles.
For example, U.S. Pat. No. 6,332,356 (DE 19815654A1) discloses an air flow meter for an internal combustion engine. The disclosed air flow meter has divided air conduits for separating dust from the sensing element. JP-2001-174305-A also discloses an air flow meter for an internal combustion engine. The disclosed air flow meter has divided air conduits.
JP-A-2001-33288 discloses an air flow meter for an internal combustion engine. The disclosed air flow meter has a short-circuit path for bypassing dust.
JP-A-2000-304585 discloses an air flow meter for an internal combustion engine. The disclosed air flow meter has louvers upstream of the sensor element.
Although the several techniques are tried and proposed, sufficient protection for the sensing element is still not obtained.